Photoelectric smoke detector with ventilation induced by light source



p il 4. 1967 s. M. FINKLE 3,312,826

PHOTOELEGTRIC S E DETECTOR H VENTILATION NDU CE I BY LIGHT SO Original Filed NOV. 19, 1962 I 2 Sheets-Sheet 1 mvsmon. \SAM M. FINKLE ATTORNEY April 4, 1967 s. M. FINKLE 3,

PHOTOELECTRIC SMOKE DETECTOR WITH VENTILATION INDUCED BY LIGH'I SOURCE Original Filed Nov. 19, 1962 2. Sheets-Sheet 2 FIG. 4

ATTORNEY 3,312,826 PHOTOELECTRIC SMOKE DETECTOR WITH VEN- TILATION INDUCED BY LIGHT SGURCE Sam M. Finkle, Long Beach, Calif.

(10351 Lampson Ave, Garden Grove, Calif. 92640) Original application Nov. 19, 1962, Ser. No. 238,545, now

Patent No. 3,226,703, dated Dec. 28, 1965. Divided and this application Dec. 28, 1965, Ser. No. 518,754

1 Claim. (Cl. 250-218) This is a divisional application of my co-pending application Serial No. 238,545, filed Nov. 19, 1962, entitled, Fire Detecting Device, which issued Dec. 28, 1965, under Patent No. 3,226,703.

The present invention relates generally to fire alarm or warning systems and concerns itself more particularly with a smoke detecting device which is capable of giving a much earlier warning than heretofore known to the art.

Fire detecting systems found in the prior art usually take the form of a smoke sensitive or heat sensitive device or a combination of both which rely principally upon the generation of, or interruption of, an electrical signal initiated by the action of either one or a combination of both of such devices.

Normally, the heat sensitive devices employed take the form of a thermostat which is used to open or close an electrical circuit to produce the required warning signal. Similarly, the smoke sensitive devices employed utilize an electrical transducer which may be one of the photo-conductor, photo-emissive or photo-voltaic types, whose current carrying characteristics are altered to effect the warning signal by changes in the intensity of light rays directed against the transducer as brought about by the presence of smoke arising from the fire to be detected.

These basic teachings have been employed in various ways in the prior art with reasonable success, but have, in the main, failed to detect fires in their incipient state. In the case of heat sensitive devices alone, the fire must have progressed to a point where suflicient heat is generated to actuate the thermostatic element of the unit, and heretofore where light sensitive devices alone were used it has been necessary that considerable smoke be present before detection was possible.

By novel structural and circuitry arrangements, I have made substantial improvements over the prior art smoke detecting devices to the end that some of the foregoing disadvantages have been overcome and the primary o'bjectives of my invention have been accomplished.

More specifically, the primary purpose of the invention, which is to provide a smoke detecting device capable of warning the presence of incipient fires, has been accomplished.

Another object of the invention is to provide a smoke detecting device which may be used with any existing heat actuated fire alarm or sprinkler supervisory system regardless of the type of control panel employed in the system.

A further object of the invention is to provide a device of the type described which when installed cannot be re moved or tampered with without causing an alarm signal to be given.

Yet another object of the invention is to provide a smoke detecting unit which is reasonably simple in construction, is easy to maintain and operate, and attractive in appearance to blend with the decor of any room or structure in which it is installed.

Other objects and advantages of the invention will become apparent as the description proceeds, and a more comprehensive understanding of the invention will be afforded from the following detailed specification when i United States Patent considered in conjunction with the accompanying drawings forming a part thereof, and in which:

FIGURE 1 is a fragmentary perspective view of a room illustrating a typical installation of the fire detecting unit of the subject invention;

FIGURE 2 is a bottom plan view of the unit;

FIGURE 3 is a perspective cutaway view showing in assembled fashion the units housing, chassis, light shield and snap-on cover, and the relative positions of its light sensitive resistors with respect to a light source and the smoke chambers formed in said chassis;

FIGURE 4 is a partial sectional view of the unit taken along the line 44 of FIGURE 2; and

FIGURE 5 is a schematic view showing the detection unit and its circuitry as invention, Like reference numerals have been used in the different views to designate like parts.

By way of general description, the invention is practiced in one of its embodiments by arranging in each of two arms of a Wheatstone bridge, a transducer or light sensitive resistor, with the other two arms of the bridge being formed, respectively, by segments of the resistance winding of a potentiometer. A low voltage, either AC. or DC, is impressed across the bridge circuit thus formed, and signal leads are taken from the sliding contact of the potentiometer as one null point and the other null point of the bridge circuit.

The bridge is then adjusted to a null condition by the potentiometer. An incandescent lamp is associated with the bridge circuit, and is mounted in a chassis in which are formed smoke chambers. Likewise, a reflecting surface mirror is mounted in the chassis so as to reflect light from the lamp through one smoke chamber to one of the light sensitive resistors, and the second light sensitive resistor is associated with its smoke chamber to receive the rays from the lamp by reflection and refraction from smoke particles in this chamber.

Thus, smoke arising from the fire to be detected is allowed to enter the first smoke chamber to decrease the intensity of light passing by reflection from the mirror to the first transducer and into the second smoke chamber to increase the intensity of the light falling on the second transducer. In this manner the bridge circuit is unbalanced and a warning signal is passed through the signal leads to a transistorized amplifier and thence through a control circuit to complete the alarm or warning.

A heat detector, taking the form of a bimetallic switch or a rate of rise type, is inserted in series with one of the transducers to detect fires which produce imperceptible amounts of smoke. This normally closed bimetallic switch opens under the influence of heat to unbalance the bridge circuit and generate the warning signal as previously described.

Referring now to the drawings, the self-contained fire detecting unit 11, FIGURE 2, of the present invention, which may be installed in a room or other enclosure 12 as shown in FIGURE 1, comprises in part a. housing 13, FIGURES 3 and 4, a chassis 14, a cover 15, and a mountplate 16.

The chassis 14 is secured to the mounting plate 16 by a screw 17 and circumferentially extending ring 18 of epoxy cement or other bonding agent,

by means of a few bayonet type hooks 13a to provide an air duct 13b between housing 13 and chassis 14, as well as other portions of the device as illustrated in FIGURE 4. The mounting plate 16 is attached to the housing 13 by countersunk screws 21. The cover 15 is removably attached to the housing 13 through the agency of a light shield 22 attached to the cover 15 by countersunk screws 23. In this instance the rounded surface 24 of the light shield 22 engages in an annulus depression 25 cut in the housing 13 to attach the cover 15 to the latter in snapon fashion.

A concentric port 26 is provided between the light shield 22 and the cover 15 which permits smoke-contaminated air to pass into the unit 11 as indicated by the arrows shown in FIGURE 4. The smoke-contained air is passed out of the unit through a series of vents 27 opened in the housing 13.

The entire unit 11 may be installed by attachment to a standard plaster ring 19 by screw headed bolts 28 passed through holes 29 (FIGURE 3) in the chassis 14- and plate 16. Housing 13 including cover 15 are concurrently removed to attain access to these screws. In the alternate, the unit may be attached by wood screws used in place of the bolts 28 which are passed through the holes 29 for direct connection to a wall or ceiling.

Within the unit 11 there is contained a heat detecting element 31 (FIGURE 4) which is retained in a centrally located bore 32 in the cover 15 to present a heat sensitive surface 33 thereof external to the unit. The element 31 is secured to the cover 15 by two screws 34 which serve as contacts.

The chassis 14, which is cylindrical in shape, has sections removed (FIGURE 3) to form two smoke chambers 35 and 36, and three receptacles 37, 38 and 39. Also, the chassis 14 has a groove 41 channeled therein extending transversely thereof to a depth of a little more than the height of the smoke chambers. A second groove 42 is also channeled into the chassis to have an open wall thereof form a common terminal end for the smoke chambers 35 and 36, and to hold a mirror as will be described hereinafter.

The receptacles 37 and 39 have mounted therein, respectively, transducers 43 and 44 which are associated respectively with the smoke chambers 35 and 36. The receptacle 38 houses an incandescent lamp 45, the light from which is diffused in the smoke chamber 36 and which is reflected from a mirror 46 mounted in the groove 42 along the smoke chamber 35, all in a manner to be described more completely herein. The groove 41 in the chassis 14 retains a glued-on translucent dust cover 47 (FIGURE 4) which protects the lamp 45 and the two transducers 43 and 44 from airborne particles such as dust, and minimizes the possibility of the tampering with the transducer and lamp. Also mounted on the chassis 14 in a compartment therein (not shown) is a potentiometer 48 shown schematically in FIGURE which has an adjustment screw or member 49 that projects outwardly through an opening formed in the housing 13 for accessibility outside the unit. This adjustment screw can be and is preferably factory set.

While no limitation on theinvention is to be inferred from the teaching pertaining to the use of any particular materials or elements, the housing 13, the chassis 14, and the cover are formed preferably from a heat resistant phenolic plastic. The light shield 22 is made of metal such as brass to give it rigidity and longer wear in performing its secondary function as the snap-on mounting for the cover 15. The mounting plate 16 may be made of micarta or some other suit-able plastic. All of the elements contained in the unit such as the lamp, potentiometer and transducers may take any suitable form of those available on the commercial market.

With reference to FIGURE 5, the electrical elements, mounted in the unit as previously described, are operatively connected as shown. Here the transducer 43, which in the illustrated embodiment takes the form of a cadmium sulphide resistor (or photo-electric cell) has connected in series with it, a bimetallic switch 51 of the heat detecting device 31 (FIGURE 4) to form one arm of a Wheatstone bridge. The transducer 44, which may also take the form of a cadmium sulphide resistor, forms the second arm of the bridge and the segmented portions 52 and 53 of the resistance winding of the potentiometer 48, together with their connecting conductors, form re- 4 spectively the third and fourth arms of the bridge circuit described as AB, BC, CD and DA.

A potential from a power supply source 54, which may be either AC. or DC. is impressed upon the bridge circuit ABCD through the conductors 55 and 56 and signal leads 57 and 58 are taken respectively from the null points D and B of the bridge circuit ABCD to a transistorized amplifier 59, with the lead or conductor 57 having a variable resistance 61 connected therein to adjust the sensitivity of the signal received by the amplifier 59.

The output of the amplifier 59 is fed to a relay which energizes an alarm circuit 63 to give either a visible or audible warning or both, or to operate a sprinkler system control. The amplifier 59 and relay 62 are external to the unit 11 as well as the power source 54. In the case of the latter, a 22-volt D.C. which is regulated to a constant voltage is preferred. However, an AC. source may be used directly or it may be rectified and regulated. A bridge-type rectifier 64 is mounted in the chassis 14. The input may vary due to the fact that the resistance of the cells will not always be the same and therefore their outputs may be going in either direction in respect to the null position. The output of the rectifier bridge will always be the same polarity and therefore not cancel out the possible different potentials from other units on the same circuit.

Within the unit, all wires connecting the above described elements are carried in runs channeled in the plastic members 14, 15 and 16. The warning signal output of the bridge circuit ABCD is carried by leads to two contact posts 65 and 66 mounted for easy accessibility on the top side of the mounting plate 16. Two other contact posts 67 and 68 similarly mounted have leads connecting them with the bridge circuitry at A and C.

The amplifier 59 receives power through the conductors 69 and 71 from the same as does the bridge circuit and lamp 45, which latter device has connected in series therewith 'a variable resistor 72 used to adjust the intensity of the light produced by the lamp 45.

The unit 11 is installed by first connecting the wires from an outlet receptacle (not shown) to their proper connecting posts 65, 66, 67 and 68. The unit is then attached to the outlet receptacle or a plastic ring (not shown) and the cover 15 is snapped into place. After the unit is manufactured and before delivery to a job site, electric current is supplied thereto, and the intensity of the light from lamp 45 is properly adjusted by the resistor 72. The potentiometer 48 is also adjusted at the factory to bring the bridge into its null state and the unit is in condition for detecting a fire and giving a warning signal.

Since in its non-detecting state no current is supplied to the amplifier, several units may be connected in parallel and the sensitivity control 61 may be employed at the amplifier input for sensitivity control.

With a unit properly installed and adjusted as described above, it is conditioned to detect a flash fire (large flames and little smoke) through the action of its heat sensitive device 31. In such case, where the temperature of the ambient air rises above a predetermined degree fixed as the setting of the devices thermostatic element, the bimetallic switch 57 opens the bridge circuit ABCD and the latter is unbalanced. Current then flows across its null points and the signal thus generated is fed to the amplifier 59. The output of the amplifier 59 energizes the relay 62 which in turn causes the control warning circuit 63 to be energized and give the alarm or effect remedial action or both.

Where the fire in its incipient state generates a large quantity of smoke and little flame, the unit is capable of detecting the fire in its very early stage, before the ambient temperature rises perceptively. Detection is effected as will be described with reference to FIGURES 3, 4 and 5.

Thus, the smoke first generated by the smouldering fire arises to enter the unit 11 through the port 26 from which point it quickly passes into and fills the smoke chambers 35 and 36. With reference to FIGURE 5, it will be seen that through the agency of the novelly arranged smoke chamber, the transducers and the mirror, the direct light rays r-r from the lamp 45 to the mirror 46 and the reflected rays r'r" from the mirror to the transducer 43 are decreased in intensity by the presence of the smoke in both chambers 35 and 36, and that conversely the light rays received by the transducer 44 are increased in intensity due to their reflection from the thousands of smoke particles in chamber 36.

Hence, the resistance of the transducer 43 increases with the decrease of light intensity directed thereon and the bridge circuit ABCD becomes unbalanced. Conversely, since the light intensity falling on transducer 44 is increased, its resistance decreases and becomes additive, circuit-wise, to the effect of the transducer 43 in unbalancing the bridge. Thus, small traces of white or light colored smoke is sufiicient to activate the detection circuitry and give a much, much earlier warning than heretofore achieved. However, the device is activated by black or dark colored smoke entering the chambers 35 and 36. Such smoke if in quantity will be substan tially opaque, and little light will be reflected to transducers 43 or 44. The resistance of transducer 43 increases, and the bridge is unbalanced, with resultant actuation of the alarm. The alarm is accordingly energized by the presence of white or light colored smoke that is transparent to a degree in chambers 35 and 36, or dark or black smoke in these chambers which may be opaque. In the operation of the device the lamp 45 will obviously heat the air inside the housing 13, with cool air from the room 12 entering the device through the port 26 as shown in FIGURE 4, and heated air in the housing escaping through the vents 27.

Although a particular embodiment of the invention has been described, it is possible that the same may be practiced in other ways. fall within the scope of the appended claim, they are to considered to be included as if described.

I claim:

In combination with a stationary wall-or-ceilingmounted fire detecting device that includes a Wheatstone bridge embodying first and second light-sensitive resis- Insofar as these other practices 4O tors as first and second legs thereof, an electrically energized source of light, an electric circuit for supplying electrical energy to said bridge and source of light, an electrically operated alarm forming a part of said circuit, a mirror, an assembly for continuously supply air that may contain smoke to said device, which assembly includes:

(a) an opaque chassis having two elongate smoke chambers therein that are in angular relationship, with said chassis supporting said mirror at the junction of said chambers and said first resistor at a first end of said first chamber, which chassis also supports said second resistor at a first end said source of light so that a beam of light therefrom falls on said mirror and is reflected onto said first resistor, with said electrically operated alarm being energized when said bridge is unbalanced by presence of smoke in said chambers to increase or decrease the intensity of said beam of light reflected to said first resistor;

(b) a mounting for supporting said chassis from a ceiling or an elevated position on a wall;

(c) a housing supported by said mounting plate and extending around said chassis, which housing and mounting plate cooperatively define vent openings therebetween, with the end of said housing most remote from said mounting plate being open;

((1) a light shield mounted in the open end of said housing;

(e) a cover attached to said light shield, which shield and cover cooperatively form a port for admitting air that may contain smoke into said chambers, with said source of light heating the interior of said chassis to the extent that cool air from the ambient atmosphere that may contain smoke is continuously drawn through said port to circulate through said chambers and discharge through said vent openings.

References Cited by the Examiner UNITED STATES PATENTS 2,604,597 7/1952 Cahusac et a1. 250218 2,877,453 3/1959 Mendenhall 340-237 3,202,826 8/1965 Greathouse 250-218 RALPH G. NILSON, Primary Examiner. J. D. WALL, Assistant Examiner. 

